http://cz.archive.ubuntu.com/ubuntu/pool/universe/g/gcc-3.3/libstdc++5_3.3.6-20~lucid1_i386.deb


but exact one I used in 2010 is here:
wget http://old-releases.ubuntu.com/ubuntu/pool/universe/g/gcc-3.3/libstdc++5_3.3.6-17ubuntu1_i386.deb

as seen in: https://forum.openwrt.org/viewtopic.php?pid=116078#p116078

